A compression/decompresson script (with optional GUI) that allows user to compress/decompress Nintendo Switch ROMs loselessly, thanks to zstd compression algorithm. The compressed file can be installed directly with supported NSW Homebrew Title Installers.
There are several ways the install the script. You can find details on installation for all of them below.\
You need to have a hactool compatible keys file in a suitable directory to use the script.\
The keys file must be located as
prod.keys file in
keys.txt in the working directory.\
It can be dumped with Lockpick_RCM.
You can also use the Windows binaries. They do not require any external libraries to be installed and can be run without installing anything. You can find the binaries in the release page.
Methods listed below requires you to have Python 3.6+ installed.
Simplest way to install would be using the following command in a terminal or a command prompt. This works on every operating system with Python 3.6 and later.\
pip3 install --upgrade nsz
If you are interested in installing the GUI for the script, you can do so by running one of the following commands. On Linux it's highly recommended to follow Running from source on Linux instead.\
Python 3.6 and Python 3.7:\
pip3 install --upgrade nsz[gui]
Python 3.8 and later: Download requirements-gui.txt and execute:\
pip3 install -r requirements-gui.txt
On Linux just clone and execute
pip3 install -r requirements.txt for the no-GUI version and
./install_linux.sh if you want GUI.
The script can also be run by cloning the repo locally. You need to install the dependencies by running the following command.\
pip3 install -r requirements.txt
GUI is optional and requires extra modules to run with GUI. To install the modules required to run GUI, run the following command on Python 3.6 and Python 3.7 on Windows:\
pip3 install -r requirements-gui.txt
nsz --help usage: nsz.py [-h] [-C] [-D] [-l LEVEL] [-B] [-S] [-s BS] [-V] [-p] [-P] [-t THREADS] [-m MULTI] [-o [OUTPUT]] [-w] [-r] [--rm-source] [-i] [--depth DEPTH] [-x] [--extractregex EXTRACTREGEX] [--titlekeys] [--undupe] [--undupe-dryrun] [--undupe-rename] [--undupe-hardlink] [--undupe-prioritylist UNDUPE_PRIORITYLIST] [--undupe-whitelist UNDUPE_WHITELIST] [--undupe-blacklist UNDUPE_BLACKLIST] [--undupe-old-versions] [-c CREATE] [file ...] positional arguments: file optional arguments: -h, --help show this help message and exit -C Compress NSP/XCI -D Decompress NSZ/XCZ/NCZ -l LEVEL, --level LEVEL Compression Level: Trade-off between compression speed and compression ratio. Default: 18, Max: 22 -B, --block Use block compression option. This mode allows highly multi-threaded compression/decompression with random read access allowing compressed games to be played without decompression in the future however this comes with a slightly lower compression ratio cost. This is the default option for XCZ. -S, --solid Use solid compression option. Slightly higher compression ratio but won't allow for random read access. File compressed this way will never be mountable (have to be installed or decompressed first to run). This is the default option for NSZ. -s BS, --bs BS Block Size for random read access 2^x while x between 14 and 32. Default: 20 => 1 MB -V, --verify Verifies files after compression raising an unhandled exception on hash mismatch and verify existing NSP and NSZ files when given as parameter -p, --parseCnmt Extract TitleId/Version from Cnmt if this information cannot be obtained from the filename. Required for skipping/overwriting existing files and --rm-old- version to work properly if some not every file is named properly. Supported filenames: *TitleID*[vVersion]* -P, --alwaysParseCnmt Always extract TitleId/Version from Cnmt and never trust filenames -t THREADS, --threads THREADS Number of threads to compress with. Numbers < 1 corresponds to the number of logical CPU cores for block compression and 3 for solid compression -m MULTI, --multi MULTI Executes multiple compression tasks in parallel. Take a look at available RAM especially if compression level is over 18. -o [OUTPUT], --output [OUTPUT] Directory to save the output NSZ files -w, --overwrite Continues even if there already is a file with the same name or title id inside the output directory -r, --rm-old-version Removes older versions if found --rm-source Deletes source file/s after compressing/decompressing. It's recommended to only use this in combination with --verify -i, --info Show info about title or file --depth DEPTH Max depth for file info and extraction -x, --extract Extract a NSP/XCI/NSZ/XCZ/NSPZ --extractregex EXTRACTREGEX Regex specifying which files inside the container should be extracted. Example: "^.*\.(cert|tik)$" --titlekeys Extracts titlekeys from your NSP/NSZ files and adds missing keys to ./titlekeys.txt and JSON files inside ./titledb/ (obtainable from https://github.com/blawar/titledb). Titlekeys can be used to unlock updates using NUT OG (OG fork obtainable from https://github.com/plato79/nut). There is currently no publicly known way of optioning NSX files. To MitM: Apply disable_ca_verification & disable_browser_ca_verification patches, use your device's nx_tls_client_cert.pfx (Password: switch, Install to OS and import for Fiddler or import into Charles/OWASP ZAP). Use it for aauth- lp1.ndas.srv.nintendo.net:443, dauth- lp1.ndas.srv.nintendo.net:443 and app-b01-lp1.npns.srv.nintendo.net:443. Try with your WiiU first as there you won't get banned if you mess up. --undupe Deleted all duplicates (games with same ID and Version). The Files folder will get parsed in order so the later in the argument list the more likely the file is to be deleted --undupe-dryrun Shows what files would get deleted using --undupe --undupe-rename Renames files to minimal standard: [TitleId][vVersion].nsz --undupe-hardlink Hardlinks files to minimal standard: [TitleId][vVersion].nsz --undupe-prioritylist UNDUPE_PRIORITYLIST Regex specifying which dublicates delegtion should be prioritized before following the normal deletion order. Example: "^.*\.(nsp|xci)$" --undupe-whitelist UNDUPE_WHITELIST Regex specifying which dublicates should under no circumstances be deleted. Example: "^.*\.(nsz|xcz)$" --undupe-blacklist UNDUPE_BLACKLIST Regex specifying which files should always be deleted - even if they are not even a dublicate! Be careful! Example: "^.*\.(nsp|xci)$" --undupe-old-versions Removes every old version as long there is a newer one of the same titleID. -c CREATE, --create CREATE create / pack a NSP
nsz -C /path/to/folder/with/roms/
nsz --verify -C /path/to/folder/with/roms/
nsz --threads 8 --output /path/to/out/dir/ -C /path/to/folder/with/roms/
nsz --level 22 -C /path/to/folder/with/roms/
nsz -D /path/to/folder/with/roms/
To view all the possible flags and a description on what each flag, check the Usage section.
NSZ files are functionally identical to NSP files. Their sole purpose to alert the user that it contains compressed NCZ files. NCZ files can be mixed with NCA files in the same container.
As an alternative to this tool NSC_Builder also supports compressing NSP to NSZ, and decompressing NSZ to NSP. NSC_Builder can be downloaded at https://github.com/julesontheroad/NSC_BUILDER
XCZ files are functionally identical to XCI files. Their sole purpose to alert the user that it contains compressed NCZ files. NCZ files can be mixed with NCA files in the same container.
These are compressed NCA files. The NCA's are decrypted, and then compressed using zStandard.
The first 0x4000 bytes of an NCZ file is exactly the same as the original NCA (and still encrypted). This applies even if the first section doesn't start at 0x4000.
At 0x4000, there is the variable sized NCZ Header. It contains a list of sections which tell the decompressor how to re-encrypt the NCA data after decompression. It can also contain an optional block compression header allowing random read access.
All of the information in the header can be derived from the original NCA + Ticket, however it is provided pre-parsed to make decompression as easy as possible for third parties.
Directly after the NCZ header, the zStandard stream begins and ends at EOF. The stream is decompressed to offset 0x4000. If block compression is used the stream is splitted into independent blocks and can be decompressed as shown in https://github.com/nicoboss/nsz/blob/master/nsz/BlockDecompressorReader.py
class Section: def __init__(self, f): self.magic = f.read(8) # b'NCZSECTN' self.offset = f.readInt64() self.size = f.readInt64() self.cryptoType = f.readInt64() f.readInt64() # padding self.cryptoKey = f.read(16) self.cryptoCounter = f.read(16) class Block: def __init__(self, f): self.magic = f.read(8) # b'NCZBLOCK' self.version = f.readInt8() self.type = f.readInt8() self.unused = f.readInt8() self.blockSizeExponent = f.readInt8() self.numberOfBlocks = f.readInt32() self.decompressedSize = f.readInt64() self.compressedBlockSizeList =  for i in range(self.numberOfBlocks): self.compressedBlockSizeList.append(f.readInt32()) nspf.seek(0x4000) sectionCount = nspf.readInt64() for i in range(sectionCount): sections.append(Section(nspf)) if blockCompression: BlockHeader = Block(nspf)
NSZ pip package: https://pypi.org/project/nsz/
Forum thread: https://gbatemp.net/threads/nsz-homebrew-compatible-nsp-xci-compressor-decompressor.550556/
SciresM for his hardware crypto functions; the blazing install speeds (50 MB/sec +) achieved here would not be possible without this.
Thanks to our contributors: nicoboss, blawar, plato79, eXhumer, Taorni, gabest11, thatch, pR0Ps, maki-chan